Increasing the credibility of the twin birth instrument

Twin births are an important instrument for the endogenous fertility decision. However, twin births are not exogenous either as dizygotic twinning is correlated with maternal characteristics. Following the medical literature, we assume that monozygotic twins are exogenous, and construct a new instrument, which corrects for the selection although monozygotic twinning is usually unobserved in survey and administrative datasets. Using administrative data from Sweden, we show that the usual twin instrument is related to observed and unobserved determinants of economic outcomes, while our new instrument is not. In our applications we find that the classical twin instrument underestimates the negative effect of fertility on labor income. This finding is in line with the observation that high earners are more likely to delay childbearing and hence have a higher risk to get dizygotic twins.     

STRUCTURAL VECTOR AUTOREGRESSIONS: CHECKING IDENTIFYING LONG‐RUN RESTRICTIONS VIA HETEROSKEDASTICITY

Long‐run restrictions have been used extensively for identifying structural shocks in vector autoregressive (VAR) analysis. Such restrictions are typically just‐identifying but can be checked by utilizing changes in volatility. This paper reviews and contrasts the volatility models that have been used for this purpose. Three main approaches have been used, exogenously generated changes in the unconditional residual covariance matrix, changing volatility modelled by a Markov switching mechanism and multivariate generalized autoregressive conditional heteroskedasticity models. Using changes in volatility for checking long‐run identifying restrictions in structural VAR analysis is illustrated by reconsidering models for identifying fundamental components of stock prices.     

Gemeinsame österreichisch-ungarische Sedimentforschung im Rahmen des EFRE-Projektes SEDDON

The multiple uses of the Danube River for navigation, hydropower production and as a drinking water supply influence its ecological quality. Flow restrictions due to regulation as well as impacts on the sediment regime such as retention in the catchment area and interruption of the sediment continuum result in changes of the hydromorphological structures and can produce major problems in the context of sediment management. In light of these facts, cross-border investigations of sediment transport at the Danube River are called for. As there are no uniform research approaches shared by Austria and Hungary, the EU-funded project SEDDON (Sediment Research and Management at the Danube River) aims to compare different monitoring and modeling techniques used to determine sediment transport, and to develop mutual solutions. Further, the laboratory equipment currently used for hydraulic model experiments is evaluated and a research channel with a free flowing discharge of up to 10 m³/s without pumping will be constructed, allowing large-scale joint laboratory tests concerning sediment to be performed.     

Erstens: ignorieren, zweitens: diffamieren, drittens: umarmen?

Mass media are an essential factor for the success of small parties, for the media can act in a supporting or an inhibiting way towards these parties. This could be observed for the example of the German Green Party: As the Greens were becoming more and more important in the parliaments, the media changed their formerly very critical view of the party to a more factual and positive reporting. Is the party “Die Linke” now experiencing a similar process? The present study analyses the comments of three national German newspapers from 2005 to 2009, using a quantitative content analysis with the aim of bringing to light how the media acted towards “Die Linke”. The results show that commenting has hardly changed since earlier studies were published. Factual issues only play a marginal role, and the party is judged negatively in all newspapers, with the tageszeitung slightly distinct from the other two papers, though.     

Auswirkungen von Baggerungen und Verklappungen hochwasserbedingter Feinsedimentablagerungen am Fallbeispiel Winterhafen Linz/Donau

In the case study “Winterhafen Linz” the effects of dredging/excavating fine sediments previously deposited by flood events and their subsequent dumping into the Danube mainstream were investigated. While this maintenance work was in progress, the temporal and spatial extent of the sediment plume and the changes in bed topography were measured. By employing air-lift samplers and grab samplers in the dredging and dumping areas, the question as to whether, and if so to what extent, the benthic invertebrate community was disturbed by the maintenance work. It could be clearly demonstrated that the sediment dredging severely affected the benthic invertebrates (an 82 % decline in biomass), while the dumping of the material had no effects on the Danube biota. Numerical modeling was used to simulate discharges and dumping locations other than those actually encountered during the monitoring campaign, thus making it possible to extrapolate and draw conclusions beyond the concrete results. These findings in turn provided the basis for recommendations on how to optimize dredging and dumping procedures on the Danube in future.     

Modelling Hospital Admission and Length of Stay by Means of Generalised Count Data Models

For a large heterogeneous group of patients, we analyse probabilities of hospital admission and distributional properties of lengths of hospital stay conditional on individual determinants. Bayesian structured additive regression models for zero‐inflated and overdispersed count data are employed. In addition, the framework is extended towards hurdle specifications, providing an alternative approach to cover particularly large frequencies of zero quotes in count data. As a specific merit, the model class considered embeds linear and nonlinear effects of covariates on all distribution parameters. Linear effects indicate that the quantity and severity of prior illness are positively correlated with the risk of hospital admission, while medical prevention (in the form of general practice visits) and rehabilitation reduce the expected length of future hospital stays. Flexible nonlinear response patterns are diagnosed for age and an indicator of a patients' socioeconomic status. We find that social deprivation exhibits a positive impact on the risk of admission and a negative effect on the expected length of future hospital stays of admitted patients. Copyright © 2015 John Wiley & Sons, Ltd.